The present invention relates to synthetic aperture radar data processing, and more particularly, to the use of interference compression to substantially remove interference from synthetic aperture radar data while minimally disturbing the desired radar data.
Synthetic aperture radars collect coherent echoes from objects primarily located on the surface of the earth. Images of these features are made using a variety of signal processing techniques. Coherent interference is present in the images generated by the terrain-imaging synthetic aperture radars. Such interference severely degrades the appearance and information content of radar imagery. Also, coherent interference occurs in carrier signals of television broadcasting stations, mobile and portable two-way radios, cellular telephone systems, and the like. Such interference also degrades the performance of these systems.
Prior to the development of the present invention, some experiments relating to radio frequency interference (RFI) removal were performed during a Government contract (Contract No. F33615-90-C-1417). These preliminary experiments did not involve any processing of the data in such a way as to compress or localize the interference and thereby facilitate its removal, nor was subtraction of interference performed.
Conventional interference removal techniques for processing synthetic aperture radar data have involved removal of long lines or large blocks of data corrupted by interference. Such techniques do not exploit the central concept of the present invention, which are interference compression to remove interference without disturbing the desired radar data, and interference removal by means of subtraction.
Prior art techniques for providing interference removal did not preferentially compress the radio frequency interference. Therefore, when interference removal was attempted, substantial amounts of radar data were lost because it was summed with interference and was indistinguishable from it. Furthermore, the conventional techniques were manual and were therefore slow and dependent upon operator skill or experimentation.
In view of the above, it is an objective of the present invention to provide for an improved method for processing synthetic aperture radar data by compressing radio frequency interference to substantially remove interference from the synthetic aperture radar data without disturbing the desired radar data.